Setting Time Zone - There's already loud about it being overzealous and draining battery. I'm more than fine with it being off as so far my iPhone deals well with time zone adjustment from network time.

Traffic - This bugs me a lot. It does not affect traffic in Maps.app and seems to be used frequently, too. What for? Any ideas?

1 Answer
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Cell network search: when in presence of two or more network antennae, probably it register which one is better where (so it has to know where), in order to automatically connect to it the next time you''ll be in the same place.

Diagnostics & Usage: possibly related to the one above, about battery life draining with different antennae

Traffic: I guess this one is to collect data for a yet to be announced product (see the Apple Q&A regarding this.